JPH0826845A - Foaming inorganic composition - Google Patents

Abstract

(57) [Summary] [Problem] To provide a foamable inorganic composition capable of obtaining a foam having excellent water resistance, high strength, low specific gravity and small heat shrinkage. [Structure] (A) Powders of fly ash, silica-alumina clay, kaolin minerals, metakaolin, etc., and inorganic powders obtained by subjecting these to thermal spraying, heating, crushing, etc., and alumina cement, γ-alumina, Reactive inorganic powder consisting of thermally sprayed alumina, alkali metal aluminate, aluminum hydroxide alumina powder, (B) alkali metal silicate, (C) aluminum powder having a particle size of 200 μm or less, (D) water A foamable inorganic composition comprising:

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a foamable inorganic composition.

[0002]

2. Description of the Related Art Heretofore, there have been proposed some inorganic compositions which are cured and foamed by heat in the presence of an alkali. For example, alkali metal silicate, metallic foaming agent,
An inorganic composition comprising fly ash or blast furnace slag and water (Japanese Patent Laid-Open No. 57-77062) has been known.

However, fly ash varies depending on the place of production and has a very low reactivity with alkali metals, so that it takes a long time to cure. Further, the foam obtained using the above composition lacks in the uniformity of cells, poor in water resistance, only a foam of low strength and low magnification is obtained, and further heat shrinkage occurs during drying, and cracks occur. There were problems such as occurrence.

[0004]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a foamable inorganic composition capable of obtaining a foam having excellent water resistance, high strength, low specific gravity and small heat shrinkage. Is.

[0005]

The foamable inorganic composition of the present invention comprises a reactive inorganic powder (A), an alkali metal silicate (B), an aluminum powder (C) having a particle size of 200 μm or less, and water ( D).

The reactive inorganic powder (A) is composed of an inorganic powder and an alumina powder. The above-mentioned inorganic powder is fly ash containing 80 wt% or more of powder having a particle size of 10 μm or less, powder obtained by melting fly ash and spraying in gas, and fly ash of 0.1 to 30 kwh / k.
powder obtained by applying mechanical energy of g, powder obtained by melting clay consisting of silica-alumina-based powder and spraying in gas, 0.1-30 kwh / k
powder obtained by applying mechanical energy of g, powder obtained by further heating the powder to 100 to 750 ° C.,
0.1 to 30 kW for metakaolin and metakaolin obtained by heating and dehydrating kaolin mineral at 500 to 900 ° C.
It is at least one selected from the group consisting of powders obtained by applying mechanical energy of h / kg.

[0007] The fly ash is JIS A 6
201 means fine ash particles collected by a dust collector from a pulverized coal combustion boiler, silica 45% or more,
Moisture 1% or less, ignition loss 5% or less, specific gravity 1.95 or more,
Specific surface area of 2700 cm ² / g or more, 44 μm standard sieve 7
5% or more passes.

As a method for obtaining fly ash containing 80% by weight or more of powder having a particle size of 10 μm or less from the above fly ash, any conventionally known method can be used, for example, sieve, specific gravity, wind force, wet settling, etc. And classification by jet mill, roll mill, ball mill and the like.

When the amount of powder having a particle size of 10 μm or less in the fly ash decreases, the alkali metal silicate (B) is used.
Since the reactivity with is reduced, it is limited to 80% by weight or more. The fly ash may be calcined if necessary. When the firing temperature is low, the black color of fly ash remains and coloring is difficult even if pigments are added,
The higher the temperature, the lower the reactivity with the alkali metal silicate (B), so 400 to 1000 ° C. is preferable.

As the clay composed of the silica-alumina powder, 5 to 85% by weight of SiO ₂ and Al are used as chemical components.
Those containing 90 to 10% by weight of ₂ O ₃ are preferable. Examples thereof include kaolin minerals (kaolinite, dickanite, nacrite, halloysite, etc.), mica clay minerals (muscovite, illite phengite, glauconite, geradonite, paragonite, plummarite, etc.), smectites (montmorillonite). , By date, introlite, savonite, sauconite, etc.),
Examples include chlorite, pyrophyllite, talc, vermiculite, wax, and shale. Examples of the silica-alumina-based powder other than the above include, for example, allophane,
Clay minerals such as imogolite, silica minerals such as quartz,
Examples include minerals such as feldspar and zeolite.

As a method for melting the above-mentioned fly ash and clay and spraying them into a gas, a thermal spraying technique applied to ceramic coating is applied. What is the thermal spray technology?
Fly ash and clay are preferably 2000-160
It is melted at a temperature of 00 ° C. and sprayed at a speed of 30 to 800 m / sec, and examples thereof include a plasma spraying method, a high energy gas spraying method, and an arc spraying method. The specific surface area of the resulting powder is preferably from 0.1 to 100 m ² / g, more preferably from 0.1~60m ² / g.

To apply mechanical energy to the fly ash and clay means to apply compressive force, shearing force, impact force and the like, and these may be acted alone or in combination of two or more kinds. As a method of applying mechanical energy, for example, a crusher generally used for the purpose of crushing, a ball medium mill (ball mill, vibration mill, planetary mill, etc.) in which impact, friction, compression, shear, etc. are combined in the crushing mechanism. ), A medium stirring type mill, a roller mill, a mortar or the like, or a jet crusher in which impact and friction are mainstream can be used.

Mechanical energy may be added dry or wet. If necessary, a grinding aid used for grinding cement clinker, silica sand, limestone or the like may be used. Examples of the grinding aid include liquids such as alcohols such as methanol and ethanol or alcohol amines such as triethanolamine, solid systems such as sodium stearate and calcium stearate, and gas systems such as acetone vapor. Is mentioned.

When the amount of mechanical energy applied to the fly ash and clay decreases, the reactivity with the alkali metal silicate decreases, and when the amount increases, the load on the crushing device increases and the wear of the device increases. Since problems such as mixing of impurities into the powder occur, 0.1-30 kwh
Limited to / kg. The mechanical energy is
The electric power supplied to the crushing device or the like when the above powder is put into operation is expressed per unit weight of the treated powder.

When the mechanical energy applied to the powder per unit time decreases, the reactivity decreases, and when the mechanical energy increases, the load on the crushing device and the like increases, and the wear of the device increases, and the mechanical energy applied to the powder increases. 0.01-40 kw / kgh because problems in production such as mixing of impurities and cost will occur.
Is preferred. The particle size of the above-mentioned powder is not particularly limited, but the average particle size is 0.
01 to 500 μm is preferable, and 0.1 is more preferable.
˜100 μm.

The method of further heating the clay to which the mechanical energy is applied is not particularly limited, and a method using any conventionally known heating device such as a gear oven or a rotary kiln can be used. When the heating temperature is low, the effect of increasing the strength of the molded product obtained from the composition of the present invention is not sufficient, and when it is high, crystallization is promoted, so the heating temperature is limited to 100 to 750 ° C, and preferably 200 to 600 ° C. is there. The heating time is
If the length is shortened, the effect of increasing the strength of the molded body is insufficient, and if the length is increased, the energy cost is increased.
5 hours is preferred.

The kaolin mineral is a 1: 1 layered silicate and has a chemical formula of Al ₂ SiO ₅ (OH) ₄ , and examples thereof include kaolinite, dickanite, nacrite and halloysite.

The method for heating and dehydrating the kaolin mineral is not particularly limited, and the same method as the method for heating clay can be used. When the heating temperature of the kaolin mineral is low, the hydroxyl groups of the kaolin mineral are not desorbed and metakaolin is not converted, and when the heating temperature is high, crystallization occurs and the alkali reactivity is significantly reduced.
Limited to 500-900 ° C, preferably 600-80
0 ° C. The heating time is preferably 5 minutes to 10 hours, because when it is shortened, metakaolin is not transformed and when it is longer, no further effect is obtained. Also, the higher the heating temperature, the shorter the heating time may be. Examples of such metakaolin include commercially available "SATINTONE S
P 33 "(manufactured by Engelhard) and the like.

The metakaolin has 0.1 to 30 kwh /
As a method of applying mechanical energy of kg, 0.1 to 30 kwh / kg is applied to the fly ash and clay.
The method of applying mechanical energy of can be used.

When the amount of the above-mentioned inorganic powder in the reactive inorganic powder (A) is small, the effect of improving heat resistance cannot be obtained,
If the amount is too large, the mechanical strength is lowered and the strength of the molded article is lowered. Therefore, it is limited to 50 to 97 parts by weight, preferably 60.
To 96 parts by weight, more preferably 75 to 93 parts by weight.

The alumina-based powder, which is another component of the reactive inorganic powder (A), is alumina cement, γ
At least one selected from the group consisting of alumina, powder obtained by melting alumina and spraying it in a gas, alkali metal aluminate salt, and aluminum hydroxide.

The above-mentioned alumina cement is a cement containing calcium aluminate as a main mineral and has a chemical component of Al
₂ O ₃ is 30 wt% or more and CaO is 50 wt% or less, and is defined in JIS R 2511. The above-mentioned γ-alumina is a general term for those having poor crystallinity caused by dehydration of hydrates other than diaspore, and examples thereof include commercially available “activated alumina” (manufactured by Sumitomo Chemical Co., Ltd.). Alumina, which is a raw material of a powder obtained by melting the alumina and spraying it in a gas, means a composition containing Al ₂ O ₃ as a main component. As a powder obtained by melting such a composition and spraying it in a gas, for example, a commercially available “Harimic” (manufactured by Micron Corporation) and the like can be mentioned. As a method of melting the alumina and spraying it into a gas, for example, a method of injecting the alumina powder into the atmosphere while melting it by flame and quenching it can be used. If the melting temperature is lowered, alumina is not sufficiently dissolved and the crystallinity does not decrease, so that the curing is not sufficiently performed.
The temperature is preferably 0 ° C or higher, and usually 16000 ° C or lower.
The injection speed is usually 30 to 800 m / sec.

The alkali metal aluminate is a compound represented by the chemical formula MAlO ₂ (M = Li, Na, K). As such a material, for example, a commercially available "Kitacleet # 10" (NaAlO ₂ , manufactured by Hokuriku Kasei Co., Ltd.) and the like can be mentioned. The above aluminum hydroxide has the chemical formula Al
It is a compound represented by (OH) ₃ . As such a product, for example, a commercially available product "C301" (manufactured by Sumitomo Chemical Co., Ltd.)
Etc.

If the amount of the alumina-based powder in the reactive inorganic powder (A) decreases, the reactivity of the reactive inorganic powder decreases, and if it increases, the heat resistance of the resulting foam decreases. To 50% by weight, preferably 4 to 40% by weight, and more preferably 7 to 25%.

Next, the alkali metal silicate (B) used in the present invention has the chemical formula M ₂ O.nSiO ₂ (M = L).
i, Na, one or more metals selected from K), wherein a dense foam cannot be obtained when the value of n in the above chemical formula becomes small, and when the value becomes large, the viscosity of the aqueous solution increases and mixing becomes difficult. Since it becomes difficult, it is preferably 0.05 to 8, and more preferably 0.5 to 2.5.

The above alkali metal silicate (B) is preferably added in an aqueous solution, and the concentration of the aqueous solution is not particularly limited, but the reactivity with the fly ash powder decreases as the concentration decreases, and solids tend to form when the concentration increases. So 10-6
0% by weight is preferred. As a method for preparing the alkali metal silicate aqueous solution, for example, the alkali metal silicate (B) may be directly dissolved in water under pressure and heating, or the alkali metal hydroxide aqueous solution may be dissolved in silica such as silica sand or silica stone powder. _{The two} components may be dissolved under pressure and heating so that n becomes a predetermined amount.

If the amount of the alkali metal silicate (B) is too small, the curing will not be sufficient, and if it is too large, the water resistance of the resulting foam will be deteriorated. Therefore, 100 parts by weight of the reactive inorganic powder (A) is used. Is limited to 0.2 to 450 parts by weight, preferably 10 to 350 parts by weight, and more preferably 20 to 250 parts by weight.

The aluminum powder (C) reacts with the aqueous alkali metal silicate solution to generate a gas, and if the particle size becomes large, a closed-cell foam cannot be obtained, so the content is limited to 200 μm or less. The above particle size is 200 μm
When the amount of the following aluminum powder (C) is small, a foam having a high expansion ratio cannot be obtained, and when the amount is large, breakage occurs. Therefore, the amount of the aluminum powder (C) is 0. The amount is 01 to 2 parts by weight, preferably 0.02 to 1 part by weight, more preferably 0.03 to 0.3 part by weight.

The water (D) may be added as the above alkali metal silicate aqueous solution or may be added alone. If the amount of water decreases, curing will not be sufficient,
Moreover, since the foaming tends to occur and the strength of the obtained foam decreases when the foaming increases, the above reactive inorganic powder (A) is used.
35 to 1500 parts by weight, preferably 45 to 1000 parts by weight, more preferably 50 to 50 parts by weight, relative to 100 parts by weight.
0 parts by weight.

In the present invention, a foaming aid may be added if necessary. The foaming aid is not particularly limited as long as it uniformly causes foaming, and examples thereof include fatty acid metal salts such as zinc stearate, calcium stearate, zinc palmitate, silica gel, zeolite, activated carbon, and porous alumina powder. Powder etc. are mentioned. These may be used alone or in combination of two or more. If the amount of the foaming aid increases, the viscosity of the composition increases, a stable foam cannot be obtained, and foam breakage easily occurs. Therefore, 10 parts by weight of 100 parts by weight of the reactive inorganic powder (A) is used. It is preferably not more than part.

In the present invention, an inorganic filler may be added if necessary. The inorganic filler is not particularly limited as long as it does not dissolve in water, does not inhibit the curing reaction of the foamable inorganic composition of the present invention, and does not react with the alkali metal silicate (B), and examples thereof include silica sand. , River sand, zircon sand, crystalline alumina, rock powder, volcanic ash, silica flour, silica fume, bentonite, mixed cement mixture such as blast furnace slag, sepiolite, wollastonite, natural minerals such as mica, calcium carbonate, siliceous Examples include soil. These may be used alone or in combination of two or more.

When the average particle size of the above-mentioned inorganic filler becomes small, the viscosity of the composition rises and a high-magnification foam cannot be obtained.
As it becomes larger, foaming becomes unstable.
00 μm is preferable. When the amount of the inorganic filler increases, the strength of the resulting foam decreases, so 700 parts by weight or less is preferable for 100 parts by weight of the reactive inorganic powder (A).

In the present invention, reinforcing fibers may be further added if necessary. As the reinforcing fiber, any one can be used depending on the performance desired to be imparted to the molded body, for example,
Examples thereof include vinylon fiber, polyamide fiber, polyester fiber, polypropylene fiber, carbon fiber, aramid fiber, glass fiber, potassium titanate fiber, and steel fiber. These may be used alone or in combination of two or more.

If the fiber diameter of the above-mentioned reinforcing fiber becomes small, it will be re-aggregated during mixing and fiber fibers will be easily formed by entanglement, and the effect of improving the strength of the finally obtained foam will be lost. Since the effect is not sufficient, 1 to 500 μm is preferable. When the fiber length is short, the effect of improving the tensile strength is not sufficient, and when the fiber length is long, the dispersibility of the fiber is reduced.
m is preferred. When the amount of the reinforcing fiber is large, the dispersibility of the fiber is deteriorated. Therefore, the reactive inorganic powder (A) 100 described above is used.
It is preferably 10 parts by weight or less with respect to parts by weight.

For the purpose of further reducing the weight of the foam, for example, silica balloon, perlite, fly ash balloon, shirasu balloon, glass balloon, inorganic natural foam such as foamed clay, phenol resin, urethane resin, polyethylene, etc. Foam of synthetic resin, vinylidene chloride balloon, etc. may be added. These may be used alone or in combination of two or more.

If necessary, aluminum powder having a particle size of more than 200 μm may be added. The addition amount is
Since a closed-cell foam cannot be obtained if the amount increases, 0.5 parts by weight or less is preferable with respect to 100 parts by weight of the reactive inorganic powder (A).

In the expandable inorganic composition of the present invention, first, the alkali metal silicate (B) is dissolved in at least a part of water (D) under pressure and heating to prepare the reactive inorganic powder (A).
And, if necessary, the remaining water (D), foaming aid, reinforcing fiber, inorganic filler, etc. are mixed to form a paste, and then the aluminum powder (C) having a particle size of 200 μm or less is added and mixed. can get. The aluminum powder having a particle size of 200 μm or less may be added in advance by mixing with a component other than the alkali metal silicate aqueous solution.

Further, as a method for obtaining a foam from the composition of the present invention, for example, the composition is foamed into a desired shape by a conventionally known method such as casting, press molding, extrusion molding, or the like, and shaped. Examples of the method include curing. The curing temperature may be room temperature, but by curing at 50 to 110 ° C. for 30 minutes to 8 hours, the curing reaction can be promoted and the mechanical properties can be improved.

[0039]

[Preparation of inorganic powder]

・ Inorganic powder 1, 2 fly ash (Kanden Kako Co., Ltd., average particle size 20 μm, JI
SA 6201) is classified by a classifier (manufactured by Nisshin Engineering Co., model: TC-15), inorganic powder 1 containing 100% by weight of powder having a particle size of 10 μm or less, and powder having a particle size of 10 μm or more. An inorganic powder 2 containing 100% by weight of the body was obtained.

Inorganic powder 3 Kaolin (SiO ₂ 45.7% by weight, Al ₂ O ₃ 38.
3% by weight, average particle size 8 μm, BET specific surface area 5.8 m ²
/ G) is sprayed at a combustion temperature of 2500 ° C. and a spraying particle velocity of 50 m / sec, and the inorganic powder 3 (SiO ₂ 49.7% by weight, A
1 ₂ O ₃ 47.0% by weight, average particle size 4.9 μm, BET
A specific surface area of 64.3 m ² / g) was obtained.

Inorganic powder 4 After melting fly ash at 3000 ° C., it was sprayed into the atmosphere at a speed of 80 m / sec, and the inorganic powder 4 (average particle size 5 μm,
A specific surface area of 9.5 m ² / g) was obtained. -Inorganic powder 5 The inorganic powder 1 was fired at 600 ° C to obtain an inorganic powder 5 containing 100% by weight of powder having a particle size of 10 µm or less.

Inorganic powder 6 Fly ash (manufactured by KANDENKA CORPORATION, average particle size 20 μm, specific surface area 1.8 cm ² / g, according to JIS A 6201) 10
0 parts by weight and 0.5 parts by weight of a mixed solution of 25% by weight of triethanolamine and 75% by weight of ethanol into an Ultra Fine Mill AT-20 (manufactured by Mitsubishi Heavy Industries, Ltd., zirconia ball 10 mm used, ball filling rate 85% by volume). Supply and apply 25 kwh / kg of mechanical energy,
Inorganic powder 6 was obtained. The mechanical energy applied was represented by the electric power supplied to the ball mill per unit weight of the treated powder.

Inorganic powder 7 Kaolin (SiO ₂ 45.7% by weight, Al ₂ O ₃ 38.
3% by weight, average particle size 8 μm, BET specific surface area 5.8 m ²
/ G) 95 parts by weight, 5 parts by weight of quartz (product name: soft silica, manufactured by Sumitomo Cement Co., Ltd.), and 0.5 parts by weight of a mixed solution of 25% by weight of triethanolamine and 75% by weight of ethanol, Ultra Fine Mill AT-20. And the inorganic powder 7 was obtained in the same manner as the inorganic powder 6.

Inorganic powder 8 The inorganic powder 7 was heated at 300 ° C. for 3 hours to obtain an inorganic powder 8. Inorganic powder 9 Metakaolin (product name: SATINTONE SP 33, manufactured by Engelhard, average particle size 3.3 μm, specific surface area 13.9 m ² /
g) Inorganic powder 10 100 parts by weight of the above inorganic powder 9 and 0.5 parts by weight of a mixed solution of 25% by weight of triethanolamine and 75% by weight of ethanol are supplied to the Ultra Fine Mill AT-20, and 10 kwh / Applying mechanical energy of kg,
Inorganic powder 10 was obtained.

[Alumina Powder] Alumina Powder 1 Alumina Cement (Product Name: Asahi Alumina Cement 1
No., manufactured by Asahi Glass Co., Ltd. ・ Alumina-based powder 2 γ-alumina (product name: activated alumina, manufactured by Sumitomo Chemical Co., Ltd.) ・ Alumina-based powder 3 Powder obtained by melting alumina and spraying it into a gas (product name: Harimic Micron Co., Ltd.-Alumina powder 4 Sodium metaaluminate (Product name: Kitakreat # 1
0, manufactured by Hokuriku Kasei Co., Ltd. ・ Alumina-based powder 5 Aluminum hydroxide (Product name: C301, manufactured by Sumitomo Chemical Co., Ltd.)

[Aluminum powder] -Aluminum powder 1 Aluminum powder containing 100% by weight of powder having a particle size of 100 μm or less (product name: 260S, manufactured by Minarco) -Aluminum powder 2 100% by weight of powder having a particle size of 70 μm or less Aluminum powder contained (product name: 350F, manufactured by Minarco) -Aluminum powder 3 Aluminum powder containing 100% by weight of powder having a particle size of 300 to 600 μm or less (product name: # 220SP, manufactured by Minarco)

(Examples and Comparative Examples) Alkali metal silicates having a predetermined amount of M ₂ O · nSiO shown in Tables 1 to 4 were used.
₂ (M = Na, K, molar ratio 1: 1, n = 1.8) was dissolved in a predetermined amount of water at 130 ° C. and 7 kg / cm ² in an autoclave, and wollastonite (product name: Chemolite A
-60, manufactured by Tsuchiya Kaolin Co., Ltd., vinylon fiber (product name: R
M182 × 3, manufactured by Kuraray Co., Ltd.) and zinc stearate were added and mixed for 3 minutes with a hand mixer. Further, a predetermined amount of inorganic powders 1 to 10 and alumina powders 1 to 5 were added and mixed with a hand mixer for 3 minutes. A predetermined amount of aluminum powders 1 to 3 was added to the obtained mixture, and the mixture was stirred for 40 minutes, poured into the mold, foamed for 3 minutes, and then heated together with the mold in an oven at 85 ° C. for 4 hours. A foam was obtained.

[0048]

[Table 1]

[0049]

[Table 2]

[0050]

[Table 3]

[0051]

[Table 4]

The foams obtained in Examples 1-27 and Comparative Examples 1-9 were evaluated as follows. The results are shown in Tables 5 and 6. 1) Compressive strength The obtained foam was cut into 30 mm × 30 mm × 30 mm, and the compressive strength was measured according to JIS A 1108. 2) Density The obtained foam is 100 mm x 100 mm x 100 mm
It was cut into pieces and weighed. 3) Strength retention after hot water test The obtained foam was cut into 30 mm x 30 mm x 30 mm and immersed in water at 90 ° C for 8 hours, and then JIS A 1
The compressive strength was measured according to 108, divided by the compressive strength before immersion, and multiplied by 100.

4) Shrinkage rate after heat test The obtained foam was 100 mm x 100 mm x 100 mm.
Cut into pieces and heat in an oven at 950 ° C for 2 hours, then
The lengths in three directions were measured at room temperature, and the shrinkage rate after the heat test was determined by the following formula. Shrinkage rate (%) after thermal test = (average length of 3 directions after thermal test [mm] -average length of 3 directions after thermal test [mm]) ÷ length of 3 directions after thermal test Average of [mm] × 100

[0054]

[Table 5]

[0055]

[Table 6]

[0056]

Industrial Applicability The foamable inorganic composition of the present invention is as described above, and it is possible to obtain a foam having high strength and low specific gravity, excellent hot water resistance and little heat shrinkage.

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display area // (C04B 28/26 22:04) 111: 40 (72) Inventor Yoshihiro Tanaka Kamitobaue, Minami-ku, Kyoto 2-2 Otokomachi Sekisui Kagaku Kogyo Co., Ltd. (72) Inventor Sadahiro Obata 2-2 Kamitobagami Tokokocho Minami-ku, Kyoto City

Claims (1)

[Claims] 1. A reactive inorganic powder comprising 100 parts by weight of (A) 50 to 97% by weight of inorganic powder and 3 to 50% by weight of alumina powder, and (B) 0.2 to 45 of alkali metal silicate.
0 parts by weight, (C) 0.01 to 2 parts by weight of aluminum powder having a particle size of 200 μm or less, and (D) water 35 to 150
0 parts by weight, wherein the inorganic powder is obtained by melting fly ash containing 80% by weight or more of a powder having a particle diameter of 10 μm or less, and fly ash and spraying it into a gas. Powder, powder obtained by applying mechanical energy of 0.1 to 30 kwh / kg to fly ash, powder obtained by melting and spraying clay composed of silica-alumina powder into gas, Powder obtained by applying mechanical energy of 0.1 to 30 kwh / kg to clay, powder obtained by heating the powder to 100 to 750 ° C., and kaolin mineral of 500 to 900
At least one selected from the group consisting of metakaolin obtained by dehydration by heating at ℃, and powder obtained by applying mechanical energy of 0.1 to 30 kwh / kg to metakaolin. Is at least one selected from the group consisting of alumina cement, γ-alumina, powder obtained by melting and spraying alumina into gas, alkali metal aluminate, and aluminum hydroxide. Foamable inorganic composition.